Electrical circuit breakers



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Oct. 20, 1959 Y. PELENC 2,909,632

ELECTRICAL CIRCUIT BREAKERS Filed June 12, 1956 ll 'IIIIIIIII'InI'III I mmzeNEys.

United States Patent ELECTRICAL CIRCUIT BREAKERS Yves Pelenc, La Buisserate-Saint-Martin-le-Vinoux,

France, assignor to Ets. Merlin & Gerin, Grenoble, France Application June 12, 1956, Serial No. 590,981

Claims priority, application France July 26, 1955 1 Claim." (Cl. 200-147) This invention pertains to electrical cricuit breakers, of the kind having a magnetic blow-out for the are formed upon the breaking of a circuit under load.

More especially, the invention pertains to improvements in such breakers as described in the copending application of Andre Latour, Serial No. 565,248, filed February 13,1956, now Patent No. 2,815,418, and assigned to the owner of the present application.

In the earlier application just referred to, a construction was disclosed providing for the automatic transfer of the load current from the main movable contact blade to an auxiliary movable contact blade during the initial stage of the circuit-breaking operation, the auxiliary blade thereupon completing a circuit for the are current through the usual magnetic blow-out coil or coils, and through the usual arc horns. Rapid extinction of the arc resulted. In a final stage of the circuit opening movement, the auxiliary blade also became disconnected from the live end or pole of the supply circuit, and took up a position in which the open condition of the breaker was signalled very plainly to any observer.

The prior construct-ion just described, and which can be studied in detail by referring to the cited application, operates very successfully where the load current being interrupted is of large or medium magnitude. However, the interruption of small currents raises some ditficulties because on the one hand the thermal effect of the small current flowing through the arc struck at the parting of the contacts is not sufiicient to drive the are rapidly into the are extinction chamber and, on the other hand, the magnetic field generated by the blow-out coil or coils is similarly too weak to cause the are readily to enter the said arc extinction chamber. In order to supplement the thermal and the magnetic effects, auxiliary blastmeans are provided by the present improvements, which on opening of the breaker direct an air blast onto the arc, forcing it immediately to enter the arcing chamber. The blast-means can be of different types, the most common consisting either of a cylinder wherein a piston compresses the air which then is directed through a nozzle onto the arc, or of a bellows which is compressed so that the air therein is driven through a nozzle integral with the bellows. In any case, the piston or the bellows must be actuated by rods or other linkages or parts driven by the movable contact assembly at the beginning of the opening stroke of the same.

I have found that a particularly simple arrangement of the blast-means can be achieved on circuit-breakers of the kind described in the above patent application, allowing one to eliminate all the additional actuating means normally used for the operation of said blast means.

The invention will now be described with reference to the accompanying drawing, in which:

Fig. l is a schematical elevational partly sectional view of a magnetic blow-out circuit breaker with an auxiliary pneumatic blast means arranged according to the invention and in its expanded state.

Fig. 2 shows the same blast-means in a compressed state,

Fig. 3 is a similar view illustrating the parts in the final phase of the circuit-opening movement, and

Fig. 4 is an end elevation of the parts as they exist in the Fig. 1 condition.

In Fig. 1, 11 is the frame of the circuit-breaker on which is mounted the arc extinction chamber 12 including a blow-out coil 13, a magnetic circuit 14 with pole pieces, the cooling plates 15, a rear arcing horn 16, and a front arcing horn 17 connected to a contact clip 18, which can receive the blade 29. 20 is the input terminal carrying the fixed contact 22, and 21 is the output terminal bearing a bracket 26 on which is pivotally mounted as at the knife 24 carrying at its free end the movable contact 23. On the blade 24 there is fixed a crossarm 27 on which is pivotally mounted. as at 28 the auxiliary blade 29 which engages the contact clip 18 connected by the, conductor 34 to the front arcing horn 17. The blade 29 is urged towards the blade 24 by a spring 31.

All of the above parts are as described in the earlier application already referred to herein. The present in vention takes advantage of the inherent relative movements of the contact blades 24 and 29 to operate a pneumatic blast device without any involved linkages or other complication. To this end, between the two blades 24 and 29 is fixed a pneumatic pump, preferably in the form of a bellows 39, provided with a blast nozzle 40 having an orifice designed to direct an air jet towards the arc, the jet being spread fanwise in the vertical plane of the arcs length. The ends of the bellows may be secured to arms or flanges on the blades, such as flange 41 in Fig. 4

The operation of the device is as follows:

When the circuit-breaker is in closed position the various parts are in the position shown in Fig. l and the current flows from 20 over 22, 23 and 24 to 21. The bellows 39 is then fully expanded and the nozzle 40 is located just beneath the point of contact of the main contacts 22 and 23. On opening, the contacts 22 and 23 part and an arc is struck. The blade 24 turns clockwise, and as the blade 29 is temporarily withheld from moving clockwise by the stop 33, the bellows 39 is compressed and the air contained in it is blown through the nozzle 40 and upward onto the are which thus is rapidly driven into the arcing chamber 12. The two blades 24 and 29 and the cross arm 27 are so designed that when the bellows 39 is fully compressed the blade 29 has terminated a downwards movement by which it becomes disengaged from the stop 33.

In the prior application, during this phase of the motion, the blade 24 encountered a lateral stop on blade 29 to drive the latter clockwise and to limit the extent to which spring 31 could pull blade 29 against blade 24. With the bellows 39 between the blades, the fullycollapsed condition of the bellows presents a substantially incompressible connection therebetween. However, a positive stop could also be employed, if desired. In any event, the positions of the parts as blade 29 leaves the stop 33 are as shown in Fig. 2.

Continuing its clockwise movement, the blade 24 bearing on the collapsed bellows now drives the blades 29 in the clockwise direction (arrow F until the whole assembly attains the final open position as shown in Fig. 3.

On closing, the blade 24 turns counterclockwise together with the blade 29, which is urged towards the blade 24 by the spring 31 until the blade 29 abuts stop 32 and is withheld. From that instant on, blade 24 moves alone towards the left, expanding the bellows 39 until the movable contact 23 abuts against fixed contact 22 and the circuit-breaker is closed. During this last phase,

blade 29 of course moves slightly upward so that its upper end is again between stops 32 and 33. The bellows 39 is now ready for a new operation.

The bellows 39 may be of metal or of any other suitable material. 'Where it has inherent resilience, the tension in spring 31 will of course be made suflicient to provide the operation described. Ifthe bellows tends normally to assume its shortest length, spring 31 may even be eliminated.

It will'be readily appreciated that the auxiliary pneumatic blast device described herein is of a most simple and dependable design, and that all actuating means commonly used for its operation have been fully eliminated, thus rendering the design of the whole breaker, as well as its maintenance, simpler and less expensive.

While the invention has been described in connection with a particular preferred embodiment, it will be understood that various minor changes and modifications can be made without departing from the spirit of the invention as defined in the appended claim.

I claim: i

In a magnetic blow-out circuit breaker of the type having an arc extinguishing chute, a magnetic blow-out circuit including a blow-out coil associated with said chute, a fixed main contact disposed at the entrance to said chute, a main contact arm pivotally mounted for movement of its free end against and away from said fixed contact, an auxiliary contact arm pivoted at one end on said main contact arm, a contact clip adapted to receive the other end of said auxiliary contact arm, together with means holding said auxiliary contact arm widely spaced from said main contact arm when the breaker is in its closed condition, and a series circuit connecting said fixed main contact through said blow-out coil to said contact clip, whereby to transfer are current from said main contact arm to said auxiliary contact arm to energize said blow-out coil during opening movement of said main contact arm towards said auxiliary contact arm; the improvement which comprises a compressible air blast source mounted directly between and engaged by said arms for automatic direct compression thereof upon opening movement of said main contact arm towards said auxiliary contact arm, and a nozzle connected to that end of said source engaged by said main contact arm, for directing the flow of air from said source towards the separation space between said fixed main contact and the free end of said main contact arm, and thence into said chute during the opening phase of said breaker.

References Cited in the file of this patent Latour .1. Dec. 3, 1957 

